What NEN 1010 asks of your cable choice

NEN 1010 is the Dutch standard for low-voltage electrical installations, up to 1,000 V AC and 1,500 V DC. It is the Dutch implementation of the international IEC 60364 series, with added Dutch clauses. The Dutch building code, the Besluit bouwwerken leefomgeving (Bbl), makes it mandatory: under article 4.199 an electricity supply in a new building must comply with NEN 1010.

The edition that applies is set out in annex II of the Omgevingsregeling. At present it is still NEN 1010:2015 with corrigendum C2:2016 and amendment A1:2020. The newer NEN 1010:2020, with corrigendum C1 since mid-2024, is the current standard, but its legal designation has been postponed. For cable in the ground the difference between the 2015 and 2020 editions matters, as shown further on. For existing buildings the Bbl still refers to the 1962 edition.

For the cable choice, chapter 43 and part 5-52 count most. Clause 433.1 links the cable to the protective device. The design current IB must not exceed the rated current In of the device, and In must not exceed the current-carrying capacity IZ of the cable. In addition, the operating current I2 of the device has to stay within 1.45 × IZ. IZ itself is given in tables 52.B.2 to 52.B.13, per installation method. Those values apply to one circuit, at 30 °C in air or at 20 °C and a soil thermal resistivity of 2.5 K·m/W in the ground.

If the situation differs, you correct with the factors from annex 52.B. Table 52.B.14 covers a different air temperature, 52.B.15 a different ground temperature and 52.B.16 a different soil thermal resistivity. Tables 52.B.17 to 52.B.21 deal with several circuits side by side: bunched, in the ground, in ducts in the ground or on a cable tray. The factors are multiplied together. With seven cables touching directly in the ground, table 52.B.18 already gives a factor of 0.45.

Two lower limits on the cross-section apply regardless of the current-carrying capacity. Table 52.2 under clause 524.1 sets a minimum cross-section for fixed installations of 1.5 mm² copper for power and lighting, and 0.5 mm² for signalling and control circuits. Clause 525 limits the voltage drop between the origin of the installation and the connection point to 5% of the nominal voltage; annex 52.G recommends 3% for lighting. On long cable routes it is often the voltage drop that decides the cross-section, not the current-carrying capacity.

For cable in the ground the editions differ. NEN 1010:2020 asks in clause 522.8.10 that a buried cable is protected or lies deep enough for damage to be unlikely. The Dutch clause 522.8.10.1 asks for a trench depth of at least 0.5 m outside buildings, and the cable has to be marked with a cover or a marker tape. The old Dutch requirement that unarmoured cable in the ground needs extra protection, such as a duct, was dropped in NEN 1010:2020. The 2015 edition, which still applies by law, does contain it. If you lay unarmoured cable in the ground without a duct, agree it beforehand with the client or the inspector.

Core colours follow NEN-EN-IEC 60445 through clause 514.3. Green/yellow is for the protective conductor only, blue for the neutral, and brown, black and grey are for the phases. The cross-section of the protective conductor is in table 54.2: up to 16 mm² equal to the phase conductor, above 16 up to 35 mm² 16 mm², and above that half the phase conductor. You may also calculate it from the short-circuit current; that result is often smaller.

NEN 1010 does not set the fire performance of cable itself. Amendment A1:2020 removed those requirements from the 2015 edition, and NEN 1010:2020 refers to the building regulations for them. They are now in the Bbl. Article 4.45a with table 4.42 sets the minimum CPR class per building use and per type of space. NEN 8012 is a tool for this, not a legal requirement. How it works out per space is covered in the article on Cca and Dca.